1. Field of the Invention
The present invention relates to an apparatus for detecting an object the image of which is taken with an imaging apparatus. More specifically, the invention relates to an apparatus capable of detecting an object in motion by deleting still portions from the image of an object.
2. Description of the Related Art
With a view to enhancing the safety and comfort of vehicles such as automobiles, it has recently been proposed that the passenger occupancy of vehicles and the state of passengers be detected and control be performed in accordance with the obtained information. A typical example of this approach is the control of an air bag device that is installed on a vehicle and activated upon crash. The air bag device is required to operate optimally in accordance with the presence or absence of a passenger, whether the passenger is an adult or a child, the posture of the passenger on the seat, the position of the head of the passenger and other conditions.
Japanese Patent Unexamined Publication No. Hei. 8-268220 describes the use of a plurality of passenger detecting sensors in an automobile to detect various states of passengers such as a standing child passenger and a passenger who is holding out a hand so that the action of an air bag device is controlled in accordance with the detected state of a passenger.
Further, Japanese Patent Examined Publication No. Hei. 5-10084 describes imaging the head of the driver of an automobile with a CCD imaging device, calculating the distance to a peculiar point to determine the position of the back of the driver""s head and automatically adjusting the position of a head rest to fit the thus determined position of the back of the driver""s head.
However, a problem with the above related art is that it is impossible to extract only the passenger-related image signals from the image signals obtained with the imaging device and that therefore no adequate information about the state, position and otherwise of passengers can be obtained in spite of the complex calculations that are performed.
An object, therefore, of the present invention is to detect portions of an object that are in motion from the image signals obtained with an imaging device.
Another object of the invention is to provide an object detecting apparatus that is capable of outputting adequate information about the state of passengers in a vehicle.
In order to achieve the above objects, according to the invention, there is provided an object detecting apparatus comprising: imaging means for imaging an object; extracting means for extracting edge images from image signals supplied from the imaging means; forming means for forming a differential image between a first of the edge images and a second of the edge images as extracted from image signals that have been picked up for the object at different times; and detecting means for detecting a state of the object on the basis of the formed differential image.
According to the object detecting apparatus of the invention, there is taken the difference between the first and second edge images as extracted from image signals that have been picked up at different times and, hence, the image in the still portions of the two images is eliminated and only the image portions in motion are extracted. Thus, portions of the background without motion that are contained in the edge images are eliminated to produce edge images that only relate to the object that is substantially in motion. As a result, information can be efficiently obtained that relates to the state, position and otherwise of the object in motion.